[FormBuilderRadioGroup] Add possibility to use vertical separator

[evanholt1]

In FormBuilderRadioGroup, there is a 'separator' arguement.
However this separator is always on the same line as the item, even if the orientation is 'orientation: OptionsOrientation.vertical'.
In the source code it is always part of a 'Row', no matter the orientation.

How Can i have a separator between the radio buttons in the vertical direction? i.e: between two radio buttons below each other?

e.x:

0 choice
--separator--
0 choice 2
--separator--
0 choice 3

instead of

0 choice   --separator--
0 choice2 --separator--
0 choice3 

[deandreamatias]

This was solved with #1106